Heap leaching provides a low-cost method of extracting metal values from relatively low-grade metal-bearing materials, and has found particular application in the processing of metal-bearing ores. Generally, in traditional heap leaching operations, an ore is mined, crushed, and then transported to a heap location where it is stacked onto an impervious pad. A suitable acidic solution is dispensed onto the heap, and the resulting leach solution trickles slowly under the force of gravity to the pad, which typically has a sloped base to allow the solution to flow into collection drains for further processing, such as, for example, in a conventional, solvent extraction/electrowinning (SX/EW) process or a direct electrowinning (DEW) process.
Bio-stimulation, in general, provides a method to improve the efficiency of heap leaching operations. That is, the introduction of a suitable bacterial strain or other microorganism into the process, such as, during an agglomeration step or via a raffinate, may result in catalyzation of the oxidation reaction within the heap. Such bio-oxidation processes typically involve the use of a cultured strain of high-concentration bacteria.
Currently known bio-stimulation heap leaching processes are suboptimal in a number of respects. For example, notwithstanding advances in bio-oxidation and agglomeration techniques, these processes generally range from being time consuming to being cost-inefficient.
Accordingly, there is a need for methods and systems for bio-stimulation heap leaching that maintain the traditional cost-efficiency and simplicity of heap leaching processes while improving efficiency and metal recovery capabilities. In addition, there is a need for effective management of biological agents that are useful in heap leaching.